1. Field of the Invention
The present patent document relates generally to automated identification of objects and more specifically to a method and system of detecting floating objects in maritime video using a mobile camera.
2. Background of the Related Art
To protect naval and commercial ships from attack by terrorists and pirates, it is critical to have automatic surveillance systems able to detect, identify, track and alert the crew regarding small watercraft that might have malicious intentions, while ruling out non-threat entities. Unfortunately, radar systems, which are widely deployed on board military and commercial ships, have limitations on the minimum detectable range, lack of sensitivity to small non-metallic targets, and limited classification ability. Such deficiencies can be mitigated by a real-time video surveillance system.
While there is abundance of intelligent video surveillance systems for ground and aerial environments, very few have been developed for maritime video surveillance especially in case of mobile sensor platforms. A significant technical challenge in maritime surveillance is the automatic detection of potential targets of interest (such as boats, rafts, buoys, swimmers) and their discrimination from irrelevant scene elements (waves, sky, land and objects thereon) under a moving camera. Computer vision has been successful in detection of moving objects in video using the background subtraction which requires the camera to be stationary. When the camera is moving, the conventional approach to target detection is to compensate the camera motion and extract foreground objects that have different motion.
In maritime scenarios, however, the background motion estimation is very unreliable either due to the lack of textures in water and sky regions or, in case of textured scenes, due to the non-rigidity and rapid appearance changes of waves. Moreover, the motion compensation approach does not detect stationary targets. The limited number of existing solutions for maritime target detection rely on some kind of high-pass filter to detect small and dim blobs in an image. However, the locality of this approach leads to numerous drawbacks including the limitation in detection of larger targets, the sensitivity to waves, sun glints or water droplets on the camera lens, the presence of land and objects thereon. There is no reliable method for detection of targets in maritime environments in the prior art. Accordingly, there is a need for better target acquisition in maritime environments.